Variation in the risk of predation may profoundly affect the evolution of anti-predator behaviours. Theory predicts that selection would favour enhanced locomotor capacity in high-risk environments, such as open habitats. An earlier study demonstrated significant intrapopulation and intersexual variation in wariness and sprint speed among the lava lizards (Microlophus albemarlensis) that was concordant with presumed risk of predation on Isla Plaza Sur in the Galápagos Archipelago. In particular, males and females from sparsely vegetated areas had greater approach and flight distances than those of more highly vegetated areas; males were also faster than females. We now compare endurance capacities of males and females from the same population on Isla Plaza Sur. We predicted the higher presumed risk of predation in the sparsely vegetated region would favour enhanced performance capacities. In addition, we predicted that sexual selection for territory defence would favour males that had the ability to flee long distances. Lizards from the sparsely vegetated area did have higher endurance than those from the vegetated area. Males had higher endurance times than females, but this difference was an outcome of body size, which was inconsistent with the sexual selection hypothesis. The significant differences in endurance between locations combined with the absence of dimorphism in performance suggest that the intrapopulation differences are an outcome of natural selection for predator escape.

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